// 表示声明一个类型，同时指定类型
let a: number;
a = 10;
a = 33;
let b: boolean = true
console.log('b :>> ', b);

function sum(a, b) {
  return a + b;
}

console.log('sum(123,456) :>> ', sum(123, 456));

console.log('sum(123,456) :>> ', sum(123, '456'));


function sum2(a: number, b: number): number {
  return a + b;
}

console.log('sum2(123,456) :>> ', sum2(123, 456));





